Kohler GP83996 4.06-Inch by 2.56-Inch ID Flush Valve Gasket

Good value for the money.

Recently I replaced the flapper and this seal in our Kohler toilet that I installed fifteen years ago. With service like that, why would I not replace them with the same original factory parts? I seemed like a no brainer. Very simple to remove the old one and install, as a crippled old man (like me) can do it. It is very well made.

Did the trick. If, like me, you have a solid toilet (tank and reservoir a single unit), have a pipe handy to easily uninstall and reinstall flush drain pipe. Otherwise, can be a bearcat. YouTube has a good video.

This gasket did exactly what it’s supposed to do and completely fixed my slow leak. It’s clearly well-made and fits the Kohler flush valve perfectly once it’s seated—but fair warning: installing it is not plug-and-play. The gasket is a VERY tight fit, which I assume is intentional for a good seal, but getting it into place takes some serious finesse. Had multiple family members try and none of use could muster enough force to get the gasket clips to pass the triangular opening in the toilet, turn, and lock into place. I assumed I had ordered the wrong part (or perhaps received a knockoff) but after spending hours watching plumbing tutorials I realized it was indeed the correct part. What worked for me was first freezing the gasket around the plastic base. You want to install it while it’s still cold, since it contracts slightly when frozen and then expands as it warms up, helping it lock itself in once secured. Before installing, I lightly lathered the gasket with a bit of Vaseline. That extra lubrication made a noticeable difference and helped it slide into the triangular slot without fighting it. From there, press down firmly while twisting it into place. Because of the shape of the plastic piece in the center, using a tennis ball to apply even, centered pressure worked great and prevented damage while giving better leverage. Once installed and warmed back up, the gasket seals perfectly—no leaks, no phantom refills. If you’re comfortable with a slightly finicky install (freezer, Vaseline, and a tennis ball), this is a solid replacement part and far cheaper than replacing the entire flush assembly.

It feels like the most midlife thing to do: a review for a toilet tank gasket! Anyway, I have a Santa Rosa one-piece toilet and the gasket was disintegrating from using cleaners in the tank itself (bad idea). This gasket fits if you put it in hot water for 5 minutes before installing it. Needs a good bit of strength for the flange to clip back onto the bottom of the tank but it works. Sure beats calling a plumber for $150!

My Kohler, Santa Rosa, one piece after more than 12 years needed a complete overhaul including the tank gasket. I read and tried a couple ideas on how to get this done but ended up with my own solution. Easy peezy once I figured it out. Prepare the gasket as shown in the pic. Compress evenly to at least half its depth with wood blocks and "C" clamps. Then into the freezer for about 3 hours. Have all components of tank ready for install then remove gasket from the assembly. Olive oil on both upper and lower surfaces will give you extra time for finite adjustments. You'll have about 3 or 4 minutes before the seal expands enough to make basic install more of a challenge. Install flat side down. Slips right into the tank with no effort. Align as necessary to be square with rear of tank then install all other tank components. By this time the gasket will have tightened substantially but with effort a little adjustment can be made if required. For me, in another 30 minutes or so the gasket swelled to a tight seal with no leaks. Some warm water into the tank could speed the process. Good luck!! It really was very easy with this procedure.

Well, I needed to let some time pass before writing my review on this product. The reason for this is not due to the gasket itself, but to how difficult it was to install it and how frustrated it left me. The gasket is pretty thick in order to create a tight seal. The existing gasket on my toilet needed replacing, so I thought this would be simple. Unfortunately, my tank is very narrow and I could not get any leverage to push the Flush Valve back onto it and get the teeth of the valve to hook under the tank. I tried for a few days, coming back after frustration levels died down, only to fail again and again. I then resorted to calling a plumber thinking for sure that he could get this in with some wisdom gained from years of experience. Alas, I left him alone in the bathroom for 30 minutes while he tried and tried to get this in there to no avail. Being a plumber who is also a problem solver, he went out to his van, took some PVC pipe, a Dremel device, a drill and four screws and created a device whose sole purpose will be to replace these gaskets. See picture for the device he made. This device allows you to easily push down on the flush valve and gasket, then turn it while keeping sufficient pressure. The plumber was worth every dollar to finally get our toilet working in our master bathroom again. In summary, the gasket works just great, but the installation is beyond difficult.

I'm glad I bought 2 of these in October 2023 because it looks like Koehler no longer supplies them. Their website says "Part Not Found - contact Customer Service." My toilet recently started leaking (infrequent gushing sound). Noticed that the GP83996 gasket was expanding and very soft. Also, the presence of bubbles on the gasket indicated leak. Very hard to install. You have to compress the gasket and turn the plastic housing at the same time. So, I soaked the gasket in hot water for about 15-minutes and it went in much easier. 5-Stars overall!

A little bit difficult to install it but it is working properly finally.

Same price as going to the local specialty plumbing store without having to spend 45 mins on the road. Fit like it should. Do not put bleach inside of your water tank to clean it. It’s why I’m having to replace this gasket.

I was able to fix my toilet for fraction of the cost estimated by "specialist". The gasket was not a problem, but had to be replaced. Works well.

Perfect fit for the Kohler system. Works well & reasonably priced.

One piece Koehler Cimarron toilet was cycling. Thought the flapper was the issue. But the gasket had deteriorated. A quarter turn clockwise to undo flapper assembly. Push down to compress gasket so flapper assembly dogs catch.